This application is directed generally to a novel and improved non-contact type of gluing system and more specifically to a non-contact gluing system for applying one or more glue patterns to a surface of a workpiece such as a die-cut cup blank, which is indexed about a generally circular platform in the process of its manufacture and assembly.
Although the present invention will be illustrated and described herein with specific reference to the problem of applying the necessary glue patterns to paper cup blanks to allow the manufacture and assembly of cups therefrom, the principles of the invention may find utility in other applications. Generally speaking, the invention may find application in applying glue patterns to surfaces of moving workpieces wherein the patterns are to be applied in a direction generally parallel to the direction of movement of a workpiece, or wherein the pattern is to be applied in some direction intersecting or in a direction not parallel to the direction of movement (arcuate or otherwise) of the workpiece.
In a typical cup-forming machine, two generally circular platforms are utilized to fabricate and assemble completed paper cups from generally flat cup blanks. The first of these platforms is typically divided into six evenly spaced sections and rotates intermittently in a stepwise indexed fashion in a circular counterclockwise direction. Each incremental movement of the machine in this fashion constitutes an index. The cup blanks are die-cut and placed on the circular table at what is generally designated Station 0. The cup is then indexed to Station 1 where a seam or pattern of glue is to be applied to form the bottom seam of the cup. Hence, this first glue pattern is generally arcuately shaped, corresponding to the generally arcuate shape of the bottom edge of the cup blank. Another cup blank is placed at Station 0 with every index of the platform or table, and likewise each cup blank on the table is advanced to the next station in numerical order with each index of the table when the apparatus is operating properly. It is of course possible to have missed blanks in which case one or more stations on the table may be empty from time to time.
At Station 2 the side seam of glue is placed on the cup. The direction of the side seam is transverse to the arcuate movement of the cut cup blank, and generally extends from the arcuate bottom edge to the arcuate top edge along the line generally radial to the arcuate curvatures to the top and bottom edge respectively. This line may not be exactly radial to the circular movement of the table or platform, but may be characterized as being in a direction generally transverse thereto; that is, in a direction which would follow a line crossing a circle, or an arc of a circle describing the direction of travel of the platform or table. At Station 3 the cup is removed from this first platform or table and transferred to a mandrel which is carried on a second rotating platform or table wherein further steps of shaping and formation of the cup are carried out. Stations 4 and 5 of the first platform or table are typically idle.
The time required for the table to rotate or index from station to station may vary for different cup sizes and types. However, once the machine speed is set for a given cup type, the indexing time and rest time at each station remain constant. Typically, the duty cycle is approximately 40/60. That is, the cup is in motion about 40 percent of the time and is at rest in one of the stations about 60 percent of the time. For example, if the machine is set up to run 120 cups per minute, then the total time of movement and at rest for the cup in each station is 500 milliseconds. That is, the cup is in motion 40 percent or 200 milliseconds of that time and at rest in a given station 60 percent or 300 milliseconds of that time.
Presently, several methods for applying glue to the cup blanks are used. Two of the most commonly used methods are what are generally referred to in the industry as glue pots and stencils. A glue pot consists of a reservoir of glue which has a rotating rubber glue wheel, a portion of which rotates inside the reservoir and the remaining portion of which projects outwardly to apply glue to the cup blank or other workpiece. The width of the rubber wheel is selected to coincide with the desired width of the glue pattern to be applied.
In presently available machines, glue pots are used on Station 1 and Station 2 to apply the respective arcuate and transversely running glue patterns. At Station 1, the glue wheel is positioned above the table at the edge of the section closest to Station 2. As the cup indexes from Station 1 to Station 2, the glue wheel is mechanically lowered onto the cup and remains there until the entire glue pattern has been applied along the bottom edge of the cup. That is, as the cup indexes, the glue wheel rolls along its bottom edge and deposits the amount of glue required for the pattern. The wheel is then lifted back up into its position in contact with the glue pot to obtain glue for the next cup.
If the radius of the cup is not the same as that of the table at the gluing point, then the glue wheel is mechanically positioned so that it follows exactly the bottom arc of the cup when the table indexes. When the cup reaches the rest position at Station 2, a mechanical arm rolls a glue wheel across the side seam of the cup, and then lifts and retracts the glue wheel to its glue pot or reservoir. The glue is applied to the cup on the stroke of the arm back toward the center of the table. The glue wheel motion is controlled entirely by mechanical gearing which is driven from the drive mechanism for rotating the table.
Each size and type of cup requires a corresponding width of glue wheel and may also require adjustment to the positioning and/or line of travel of the glue wheel at respective Stations 1 and 2 to apply the correct pattern. With the mechanical controls of the glue pots, both gluing operations are performed at Station 1 and Station 2 with each index of the table, regardless of the presence or absence of a cup blank. Hence, in the event a cup blank is not supplied at Station 0, the glue pattern is applied to the top of the table at each of the Stations with the mechanical type of control currently available. This is undesirable in that the process must then be stopped to clean the top of the table.
The gluing process using stencils may also be used to apply patterns in the desired configuration at Station 1 and Station 2. A stencil which is the exact dimensions of the glue pattern to be applied is connected to a glue reservoir. At Station 1, when the cup is in the rest position, the stencil is stamped on to the cup, thus producing the arcuate bottom glue pattern. The stencil is then lifted back to a position above the cup where it is resupplied with glue from its reservoir. A second stencil at Station 2 having the dimensions of the side seam glue pattern is applied to the cup in the same manner when the cup is at rest at Station 2. The rate at which the stencils are applied to the cup is a function of the rate at which the table is indexed. Moreover, each different cup style and/or size has to be fitted with a corresponding matching stencil size for each of the two stencils. As with the glue pot technique, stencils are mechanically controlled by the table movement and are activated at each table index regardless of the presence or absence of a cup.
As indicated above, both the glue pot and stencil processes of cup gluing are controlled by a mechanical gearing which is driven from the motion of the table or platform itself. Accordingly, to change a machine set up from one style or size to another, it is necessary to change all of the related mechanical gearing, as well as either the wheel sizes and positions or directions of travel or the stencil sizes and positions. Due to the complicated mechanical gearing of the apparatus, such a changeover may take a skilled mechanic several days to accomplish. Hence, a relatively expensive piece of equipment must stand idle during the changeover, and a great deal of time and labor by relatively skilled personnel is required to accomplish the changeover.
Briefly, following the application of glue patterns to the generally flat cup blanks, the blank leaves the indexing table at Station 3 and is wrapped around a mandrel that has dimensions similar to that of an assembled cup. Compression is applied over the side seam of the cup on the mandrel by a mechanical arm. The mandrel is indexed in a clockwise direction to succeeding stations at which the cup is formed to completion before being stacked with completed cups. The compression on the side seam is done while the cup is stationary in Station 2a. When the cup is indexed to Station 3a, a fanning action is applied to the bottom of the cup on the mandrel. This creases the edge so that it can be folded over at the next Station 4a. At Station 4a, a stamping action is applied to the bottom of the cup. This compresses the glue pattern and fully forms the bottom of the cup. Heat is often applied at this station to insure a good glue bond.
At Stations 5a and 6a, the cup remains idle through each indexing period and continues to be compressed. At Station 7a the compression arm is lifted and cup is removed from the mandrel and delivered by air pressure through a curved tunnel to a station where the lip of the cup is rolled. Heat may also be applied at this station to aid the development of the lip. The cup, now fully formed, is again shot by air to a station where it is stacked. The cups are coated and are ready for use after they are removed from the stacking station. At a rate of 120 cups per minute, a new fully formed cup arrives at the stacking station every 500 milliseconds. Hence, each cup is completely formed in approximately 12 seconds. Typical cup rates, using this process range from 60 cups per minute to 180 cups per minute.